There are many applications where the separation and recovery of particulate material from bulk waste material and untreated run of the mine material (R.O.M.) would be economically and ecologically desirable. An example of this is the mounds, tips or slag heaps erected and being erected by the mining industry and composed of what was or is considered to be waste material produced in the winning of a mineral from the mine. Such tips, slag heaps or ponds contain quite large proportions of the mineral concerned but in a form which, at the time the reject reserve was being created, it was not considered viable to recover. Generally speaking, the mineral in the slag heaps and ponds is of particulate form and of such a small size that it was not thought possible to recover it economically.